High speed direct writing cathoderay tube



`lime 25, 1963 N. F. FYLER HIGH SPEED DIRECT WRITING cATHoDE-RAY TUBE Filed March 22, 1960 m\\wm EN United This invention relates to a high speed direct writing cathode-ray tube and more particularly to a high speed direct writing cathode-ray tube including a non-planar character stencil for shaping a high density cathodearay electron beam to the contiguration of the selected character.

In modern high speed electronic computer applications, as well as in numerous other applications, there is a constant need for high speed visual intelligible display of coded information. In the prior art, many mechanical and electro-mechanical printing and display devices have been utilized for this purpose. However, all of these devices have substantial inherent iner-tia which severely limits the speed of operation of the devices.

In order Vto avoid the foregoing described speed limitation of mechanical type printing and display devices there have been developed in the prior art specialized types of cathode-ray tubes capable of displaying visual characters, such as alphabetic and numeric characters, on a phosphor screen or for printing the characters on paper or other material which is moved past the face of the tube. Structurally, the cathode-ray writing tubes of the prior art are similar to conventional cathode-ray tubes except that they also include a planar character stencil positioned therein, the stencil having a number of apertures shaped in the form of characters located at various points thereon.

Referring more particularly to the structure of these specializedftubes, attention is directed to U.S. Patent No. 2,889,547, issued lune 2, 195,9, to C. A. Wesley. The Wesley patent discloses a representative prior art cathode-ray writing tube having a phosphor on its face for visually displaying the selected characters. As described in the patent, the specialized tube includes a deflection system operable under the control of la coded information signal from a magnetic memory for deflecting the cathode-ray tube electron beam from its normal path to pass through a selected one of the apertures on the stencil.

In addition, the Wesley tube includes a convergence coil positioned between the stencil and the tube face to prevent divergence of the electron beam after it has passed through the stencil. Further, the -tube includes a pair of post stencil deflection plates which operate in conjunction with a pair of corrective signal generators responsive to the coded intelligence signal for applying a correct-ive force to the electron beam after it has passed through the character stencil to compensate for the difforen-ces in path experienced by the electron beam due to the ldiiiering amounts of deliection required for the beam to pass through the different apertures on the stencil. As a result of this corrective system the beam from the stencil strikes the face of the 'cathode-ray tube at the proper position regardless of which aperture the beam has passed through.

A cathode-ray writing tube similar to the Wesley tube is disclosed in U.S. Patent No. 2,777,745, issued on January 15, 1957, to J. T. McNaney. However, the face of this tube differs from the phosphor screen of the Wesley tube in that instead of the phosphor screen, the face has a plurality of Wire segments or conductors extending from the interior of the tube through the face of the tube to the exterior surface of the face. These rates Patent `it passes through the stencil.

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Wire 4conductors are disposed substantially parallel to one another, are of small diameter, and are spaced from each other in accordance with the size of the electron beam generated by the tube.

An associated backing plate or electrode is positioned adjacent the ends of the wire conductors exterior the tube whereby the conductive wires and the plate operate as electrodes of a capacitor. It is easily understood that when the electron beam having the selected shape contacts the selected wire conductors, it charges the wires Iin accordance with the selected shape or pattern of the beam, Therefore, if a dielectric sheet is moved between the exterior ends yof the wire ysegments and the associated electrode, an electrostatic iield produced by the selected charged wires will induce a charge on the portions of the dielectric sheet adjacent the charged wires. The charge pattern on the sheet is then processed to produce a visual image in any one of a number of ways. For example, pigmented plastic powder can be sprinkled over the paper which will adhere to the charged areas whereby the characters are permanently printed on the paper. It is clear, of course, that the characters printed on the dielectric paper are :determined by which one of the many apertures on the stencil the electron beam has passed through. For example, if the electron beam passes through an Iaperture which has the shape of the numeric character 1, the electron beam is shaped to the form of the character 1. Hence, a charge is developed `on the wire segments which define a character l pattern and the charge pattern from the wire conductors `also has the pattern of the character 1.

While the foregoing described prior art cathode-ray writing tubes are capable of printing speeds far in excess of the conventional mechanical and electro-mechanical systems, the speed of printing of the prior art cathoderay writing tube is also limited by the lfact that it takes a predetermined time interval :for the electron beam to build up a sufficient charge on the wire conductor to produce a satisfactory charge pattern on the dielectric paper, the time required for a wire conductor to reach a sutlicient state .of charge being dependent on the intensity of the electron beam. However, in the prior art tubes, the intensity of the electron beam is limited by the fact that a substantial portion of the beam contacts the planar stencil, which in turn experiences thermal expansion in in direct proportion to the intensity of the electron beam. It has :been found that thermal expansion of the planar stencil causes it to distort in an unpredictable manner whereby the :apertures therein move out of registry with the tube rdeflection system in an unpredictable manner. As ya result, only portions of a selected character are printed, or in more severe cases, no character is printed at all. ln fact, in some severe cases it is even possible that the wrong character would be printed. In View of the foregoing, it is most important to keep the intensity of the electron beam relatively small in order to minimize thermal expansion of the stencil, and hence the printing speed of the prior art tubes is inherently limited.

In addition to the foregoing limitation, the characters produced by the foregoing type tubes are distorted in shape to some degree due to the fact that the electron beam does not pass through the apertures normal to the plane of the stencil. Therefore, the electron beam is shaped to conform to a projection of the aperture configuration rather then the real configuration of the aperture.

Still another very serious limitation of the `above-described prior art tubes is that the tube itself must include post-stencil deliection plates and associated energizing apparatus to insure convergence of the electron beam after More particularly, there must be associated with the use of the tubes complicated corrective circuits or generators for generating corrective signals which when applied to the post-stencil detlection plates corrects the path of the electron beam after it leaves the stencil so that the beam has a uniform path regardless of which aperture the beam passed through. It is clear, of course, that the corrective circuits must be capable of determining through which aperture the electron beam has passed and of applying unique correction signals, in accordance with which aperture the beam passed through, to the post-stencil dellection mechanism to deilect the electron beam to the uniform path.

In View of the foregoing comments it is -apparent that the prior art types of cathode-ray writing tubes are inherently limited in speed as well as in the clarity of image produced. Furthermore, not only must the prior art tubes include complex structure to insure that the electron beam remains in convergence and to correct the path of the beam after it has passed through the selected aperture in the stencil but, in addition, extensive electronic circuitry must be utilized in conjunction with the tube to properly correct the path of the electron beam.

The present invention overcomes the foregoing enumerated and other limitations of the prior art devices by providing an improved high-speed cathode-ray writing tube which can be mechanized and utilized in a simplified manner in comparison with the prior art devices. More particularly, in the tube of the present invention, a nonplanar character stencil is utilized whereby relatively large electron beam currents can be used without alecting the operation of the character stencil. Further, the tube can be mechanized without the necessity of the prior art convergence apparatus .and position deflection plates as well as their associated signal generators.

In accordance with one concept of the present invention, a convex-shaped character stencil is utilized with a deflection system capable of deecting the electron beam to pass through a selected one of a number of apertures in the convex face of the stencil normal to a plane defined by the edges of the selected aperture whereby the electron beam is automatically convergently channeled toward a predetermined point regardless of the location of the aperture through which it has passed so that the necessity for complex corrective apparatus is eliminated.

In .accordance with a further concept of the invention, a convex non-planar stencil is utilized which is responsive to thermal expansion to increase or decrease its radius of curvature uniformly about an aperture whereby the aperture remains in registry with the dellected electron beam. Moreover, the fact that the electron beam is passed through the selected aperture normal to the plane defined by the edges of the selected aperture insures that the shape of the beam is exactly the same Aas that of the selected aperture.

In accordance with one embodiment of the invention, .a cathode-ray printing tube having an electron beam generator for generating an electron beam positioned at one end and a target face at the other end includes a conductive convex-faced character stencil having a constant radius of curvature with a pltuality of dierent character apertures arranged in columns and rows therein, and a pair of horizontal and vertical electrostatic deflection plates positioned between the gun and the stencil for selectively deflecting the electron beam to pass through a selected one of the apertures. Further, the tube includes an annular-shaped insulating surface circumscribing the stencil.

In accordance with the invention, the annular-shaped insulating surface co-operates with the conductive surface of the stencil to which a voltage potential is applied, to generate an electrostatic field which curves the path of the deflected electron beam whereby the beam passes through the selected aperture normal to the plane dened by the edges of the selected aperture. Hence, the electron beam is directed toward the center of curvature of the convex stencil regardless of which aperture the beam passes through. In addition, an accelerating electrostatic eld is produced by an annular conductive coating positioned on the tube envelope between the stencil and the face of the tube which diverts the electron beam from its path toward the center of curvature and directs the beam toward the face of the tube, the magnitude of the accelerating voltage being chosen so that instead of converging -at the center of curvature, the electron beam converges at or near the face of the tube whereby the beam strikes the tube face within a predetermined area regardless of which aperture the beam passed through.

In accordance with the invention, the tube face preferably has a conductive mosaic incorporated therein comprising an array of conducting wires insulated from one another and running from the inside of the tube to the exterior face so that when the electron beam strikes the interior ends of the conducting Wires a charge pattern is established on the exterior ends of the wires. An associated electrode or plate is positionedadjacent the exterior ends of the conducting Wires and a dielectric sheet is passed between the exterior ends of the conductive wires and associated electrode. As the paper moves past the mosaic, the wires that have been charged by the electron beam convey a charge on the portions of the dielectric sheet adjacent the charged wires so that a charge pattern is produced on the paper having the configuration of the character to be printed. This charge pattern may thereafter be developed by dusting the paper with a pigmented plastic powder which adheres to the charged areas.

In a modied embodiment of the invention, a funnelshaped or frustro-conical conductor having `an aperture therein is positioned between the stencil and the tube face and an additional accelerating voltage is applied toy the funnel-shaped conductor whereby an electrostatic iield is generated which causes the electron beam to be convergently channeled through the funnel aperture .and accelerated along a predetermined path to the tube face. It should further be noted that the funnel-shaped conductor functions to converge the electron beam at a point closer to the stencil than would'be the case if the stencil were not utilized so that the overall length of the cathoderay tube of the invention may thus be reduced.

It is, therefore, an object of the present Iinvention to provide a high speed cathode-ray .printing tube utilizing a non-'planar character stencil.

It is another object of the present invention to provide a high speed cathode-ray printing tube wherein the cathode-ray electron beam passes through a selected apenture in the character stencil normal to the plane defined by the edges of the aperture whereby an undistorted character is printed'.

It is Ia further object of the present invention to provide a lhigh .speed cathode-ray printing tube utilizing a convex-faced character stencil.

It is a still fur-ther object of the present invention to utilize a convex-shaped character stencil in conjunction with a funnel-shaped conductor which convergently channels the electron beam from the character stencil along a predetermined path toward the cathode-ray tube face.

It is still another object of `the present invention to provide a character stencil which can withstand thermal expansion without the apertures thereon moving out of registry.

The novel features which are Ibelieved to be characteristic of the invention, both `as to its organization and method of operation, 'together with further objects and advantages thereof, will Ibe better understood from the `following description considered in connection with the accompanying drawings in which several embodiments of the invention are illustrated by way of example. It is to be expressly understood, however, that `t'he drawings are for the purpose of illustration and description only, and are not intended as a delinition of the limits of the invention.

FIGURE l is a diagrammatic View, partly in section, of `a cathode-ray writing tube in accordance with the invention;

FIGURE 2 is an isometric View of a character stencil in accordance with the principles yof the present invention; and

FIGURE 3 is a partially sectionalized view of a second embodiment of a cathode-ray writing tube in accordance with the present invention.

Referring now to the drawings wherein like or corresponding parts are designated by the same reference character throughout the several views, there is` shown in FIG- URE l a partially sectional-ized view of one embodiment of a high speed direct writing cathode-ray' tube of the invention, generally designated which is `operable along with associated electrical and mechanical apparatus to print at an extremely rapid rate clear and undistorted characters on the surface tof a dielectric recording medium 11, `whic-h may be paper, for example. More particularly, an `electron beam 13 generated by a conventional electron g-un 15 within ian evacuated envelope 16 is dellected from its normal path by two successive pairs of dellection plates 17 and 19 to pass through a selected one of a plurality of character apertures in a convex stencil 20 whereby the electr-on beam is shaped to conform to the configuration of the selected aperture. Hence, when the beam strikes a tar-get mosaic 21 formed by a plurality of Wire conductors 23 imbedded in the tube face plate and extending therethrough from the inside of the tube to the exterior thereof, selected wires of the plurality of the wire `conductors lare electrically charged, the geometric pattern of the conductors being charged conforming, of course, to the coniiguration of the selected aperture.

As shown in `FIGURE 1, an associated electrode 25 is connected Ito a source of ground potential and is positioned in proximity to the exterior ends of wire conductors 23 so that conductors 23 and electrode 25 act effectively as the electrodes tof a capacitor between which dielectric paper 11 is passed, .the electrostatic iield produced by the charged conductors 23 thereby inducing a charge `on the portions of the dielectric paper in proximity to each of the charged wire conductors. The charged areas on paper 11 may be developed thereafter by passing the paper over a p-owder box 27 which spr-inkles a pigmented powder over the surface of the paper, the pigmented powder adhering through electrostatic force to the charged areas whereby a character is visually produced on the surface of paper 11. In order to insure that the pigmented dust 'will not 'be removed by mechanical forces such as by the paper rubbing `against external materials, the surface of the paper may be iixed by heating and deposition of a thin hot layer of Wax which hardens upon cooling, thereby mechanically Ialfixing the pigmented po-wder to the surface of Ithe paper.

Referring now more particularly to the selection process by which it is determined which character is to be printed on paper 11, the operation of deflection plates 17 and 19 in conjunction with a pair of character selection circuits 31 and 33 will be considered. As indicated in FlGURE l, character selection circuits 31 and 33 'are responsive to a pair of coded bin-ary information signals 35 and 37, respectively, for producing bilevel deilection voltages. When the bilevel delleotion vol-tages are applied to the deflection plates 17 and 19, it is apparent that electron beam 13 can be deflected to take any one of four dilerent paths to stencil 20.

With reference now to FIGURE 2, wherein there is shown a three-dimensional view of stencil Ztl including four apertures each having the shape of a dilferent numeric character. By proper design of character selection circuits 31 and 33 deection voltages can be produced having magnitudes such that the electron beam is deflected to pass through a selected one of the four apertures in accordance with the levels of the bilevel coded intelligence or information signals 35 and 37.

It is obvious, of course, that while the stencil is shown herein as having only four apertures thereon, any number of apertures can be located on the face or surface of the stencil arranged in almost any order. For example, a stencil having 64 character apertures thereon can be easily arranged by having eight horizontal rows with each row having eight apertures therein. It should be noted that the capability of producing 64 different characters any value of a six bit weighted binary number can be uniquely represented. It will also be recognized that the deflection system for use with the 64 character aperture stencil should be capable of dellecting the electron beam to 64 different paths and could employ either a relatively large number of deilection plates energized by bilevel signals, or a relatively small number of deflection plates energized by multilevel signals. Alternatively, it will also be appreciated that magnetic deflection could be employed in lieu of electrostatic deflection. A detailed discussion of the structure `and mode of operation of one of the many types of character deflection circuits` capable of -dellecting the 4electron beam to any one of 64 different paths is disclosed in U.S. Patent No. 2,889,547, issued to C. A. Wesley on June 2, 1959. Further, another one of the many types of such a detlection system is described in the Research & Development Report 605 yof the U.S. Naval Electronics Laboratory, San Diego, California, by C. H. Cash `and W. R. Dawirs, dated June 17, 1955.

Examining now the path of the electron beam after it has been deiiected by deflection plates 17 and 19, it may be seen from FIGURE l that if there were no further modifications of the path of beam 13, it would not strike the face of stencil 2b* normal to the plane defined by the edges of any aperture which could be positioned to intercept the beam. Hence, the electron beam energizing from any such aperture would have a cross sectional configuration conforming to a projection of the aperture shape, as it appears on a plane which is normal to the path of the electron beam. Therefore, the configurations of the character to be printed would be distorted and the resulting visual image produced on paper r11 would be unclear. Furthermore, it is clear from FIGURE l that if the electron beam passes through the selected aperture without any modic-ation of its path, the electron beam would be diverging as it moved away from the stencil and toward the target mosaic 21 rather than converging so that complex apparatus would be necessary to reconverge the electron beam to insure that it would strike the target mosaic at the proper spot regardless of which of the apertures the beam passed through.

The operation of non-planar conductive stencil Ztl of the invention to eliminate the necessity for the abovedescribed prior art converging apparatus will now be described. As is shown in FIGURE l, electron beam 13 is responsive to Ian electrostatic eld generated by non-planar curved stencil 20 for changing its path to pass through the selected aperture on the stencil orthogonal to the plane deined by the edges of the selected aperture whereby the electron beam is directed toward the center of curvature of the stencil regardless of which aperture has been selected. Therefore, the necessity for the prior art converging apparatus is eliminated.

The nature of the foregoing mentioned electrostatic field is indicated in FIGURE l by the dashed equi-potential lines. As indicated in FIGURE 1, near the convex face of the stencil the lines have the same curvature as does the stencil. However, as the distance from the stencil increases, the lines increase in curvature. Therefore, since the electron beam tends to cross the equipotential lines orthogonal thereto a force is applied to the beam as it approaches the stencil which at iirst tends to make a substantial change in the path of the beam but as the beam approaches the stencil the force applied thereto tends to make less drastic changes in the beam path so that the minor path changes which are necessary to insure that the path of the beam is orthogonal to the plane defined by the edges of the selected aperture as it passes therethrough can be accomplished.

On the other side of the stencil the lines near the stencil have fthe same shape as does the stencil. However, as shown in FIGURE l, the lines start to curve the other Way at relatively small distances from the stencil whereby the beam is directed in a manner shown in FIGURE 1 so that in the absence of any other deflective forces the beam follows a generally delined predetermined path to the mosaic regardless of which aperture was selected. While not shown in FIGURE 1, the beam may be deflected by additional magnetic or electrostatic detiection apparatus as it moves along the predetermined path, so that the beam may be made 'to sweep selectively across the mosaic face to write lines or rows of characters thereon.

Referring now with particularity to the manner in which the electrostatic held is generated, it shoul-d iirst be noted that in the prior art a conductive surface generally covers substantially all the interior surface of the tube envelope and has a voltage applied thereto so that the surface acts as an accelerator for the electron beam and also as a sink for secondary electrons. In accordance with the teachings of the present invention, on the other hand, this surface is modified by separating the conductive surface into a pair of two separate areas 41 and 413, each area being insulated from the other by an insulating surface 44 positioned therebetween, as shown in FIGURE 1. As indicated in FIGURE 1, three voltage signals from a signal source 39 are applied to stencil 20 and conductive areas 41and 43, respectively. The magnitudes of the voltages applied to the stencil and the conductive areas are dependent, of course, on the distance between the stencil and the conductive areas on `the sides of the rtube, as well -as on the configuration of the stencil. With a convex stencil of the type shown in FIGURE l, it should be noted that satisfactory operation has been obtained with a voltage on stencil 20 somewhat greater than the voltage applied to area 41 and with the accelerating voltage of area 43 being substantially greater than either of the vother voltages.

In mechanizing the conductive areas 41 and 43, any of the graphite preparations known in the ant can be used to form the conductive surfaces if a non-conductive glass envelope is used. One such preparation is manufactured by the Acheson Colloids Co. of Port Huron, Michigan, and sold under the trademark Aquadag. It should be noted that if a conductive metal envelope is used, provisions for insulating conductive areas 41 and 43 from each other should be made. If the metal surface itself is used as conductive areas 41 and 43, the metal must be separated adjacent insulator 44 by some insulating material, such as glass.

Continuing with the discussion of the invention, attention is now directed to the mosaic target. As has been hereinbefore stated, the mosaic includes a group of wire conductors placed parallel to `one another in an insulating media having a low dielectric, such as glass. Further, the inductors must be imbedded in the insulator in such a manner that the overall mosaic structure is vacum tight, 'while the mosaic itself must be sealed to the tube envelope in a vaccum tight manner. In operation, the individual conductive wires of the mosaic provide a conductive path whereby the electrostatic charge produced on the ends of the conductors on the inside face of the tube by the electron beam are transferred to the exterior of the tube so that the rapid printing operation can take place. In connection with a detailed description of the mosaic structure attention is directed to copending U.S. patent application, Serial No. 16,734, for High Speed Direct Writing Cathode-Ray Tube, tiled on March 22, 1960, by N. F. Fyler.

It should be noted that beam currents of the intensity used in the present invention could never be used in prior art tubes utilizing planar stencils since substantial pontions of the electron beam necessarily strike the surface of the stencil surrounding the selected aperture, and in the prior art planar stencil the expansion due to the increase in stencil temperature resulting from the electron beam bombardment results in an unpredictable bending and buckling of the stencil so that the character aperitures move out of registry =with the deflection system. In addition, since this movement is of an unpredictable nature, it is impossible to utilize compensation methods to maintain the deflection system in registry with the stencil apertures. Hence, prior ant tubes will not function properly with electron beams having intensities corresponding to the intensities utilized in the present invention.

In view of the foregoing description, it is apparent that the writing tube of the present invention is capable of utilizing higher intensity electron beam currents than prior art tubes whereby the ultimate printing speed of the present invention is substantially greater than that of the prior art devices. 'In addition, as has been heretofore discussed, the focusing structure of the present invention is substantially simplified in comparison with prior art devices, while providing character representations substantially free from distortion.

It is evident that numerous modiiications and alterations may be made in the foregoing described embodiment of the invention. For example, while the overall length of the iirst embodiment of the invention is relatively small, there may be a limited number of applications where it is desirable to reduce the overall length of the cathode-ray tube of the invention. This may be accomplished by adding a converging funnel or nozzle between stencil 20 and mosaic 21 to hasten the convergent channeling of the electron beam whereby the distance between the stencil and the mosaic can be reduced.

Referring now to FIGURE 3, there is shown another embodiment of the invention whose overall length is less than that of the lrst yembodiment of the present invention, the second embodiment of the invention including the elements described in connection with the iirst embodiment, and in addition, a conductive converging funnel or nozzle 45 inserted between stencil 20 and mosaic 21, the nozzle including a central aperture `47. As is shown in FIGURE 3, a voltage potential from source 39l is applied to the conductive surface of funnel 45 whereby funnel 45 generates an electrostatic lield that cooperates with the electrostatic iield generated by stencil 20 and conductive coatings 41 and 43 to bend the electron beam to follow a path along the longitudinal axis of the funnel, which is also the longitudinal axis of the tube, and out aperture 47. Thereafter, the electron beam follows a predetermined path along the longitudinal axis of the tube to mosaic 21. While the course of the electron beam in the second embodiment of the invention is substantially the same as that described in connection with the first embodiment of the invention, it should be noted that the elect-ron beam converges to follow the predetermined path along the longitudinal axis of the tube at a faster rate than the second embodiment of the invention so that the `distance between stencil 20 and mosaic 211 can be substantially reduced.

It will be recognized that numerous additional modifications and alterations may be made in the cathode-ray writing tube herein described without departing from the spirit or scope of the invention. For example, mosaic target 21 could be `replaced by a conventional tube face having a phosphor on the inside surface whereby visual characters could be produced and then printed by an xerographic process. Further, it is clear that a complete line of character information can be written with the tubes of the present invention simply by placing an electromagnetic deflection coil around the outside of the tube between the stencil and the mosaic target for defiecting the electron tube to trace a line on the mosaic target. Accordingly, it is to be expressly understood that the scope of the invention is to be limited only by the scope of the appended claims.

What is claimed as new is:

1. ln a cathode-ray writing tube wherein a relatively high intensity electron beam is utilized to actuatc a target to produce an output signal representative of a character selected in accordance with a coded intelligence signal, the combination comprising: beam shaping means having a non-planar surface with a predetermined number of character apertures positioned therein, said beam shaping mea-ns including apparatus responsive to the coded intelligence signal for deiiecting the electron beam to pass the electron beam through a selected one of the character apertures substantially orthogonal to a plane defined by the edges thereof; first means operating in conjunction with the beam shaping means for convergently directing the electron beam from the selected character aperture along a predetermined path to the target whereby the target is actuated to produce the output signal having the configuration of the selected character aperture.

2. In a cathode-ray writing tube wherein a relatively high intensity electron beam is utilized to produce an output signal representative of' a selected character, the combination comprising: beam generating means selectively operable for generating an elect-ron beam; a nonplanar character stencil having at least first and second character apertures therein; and deflection means operable for selectively deflecting said electron beam to pass through a selected one of said first and second character apertures to conform the shape of said beam to that of the selected aperture.

3. ln a cathode-ray writing tube, the combination comprising: electron beam generating means for selectively generating an electron beam; a convex faced character selection stencil having a constant radius of curvature, said facing having a pair of character apertures positioned therein at a predetermined pair of positions, respectively; beam deflection means for directing said electron beam through a selected one of said pair of character apertures and radially toward the center of curvature of the convex faced stencil; first means for deilecting said electron beam from its radial path to follow a predetermined path which is independent of the character aperture through which the beam has passed; and target means responsive to the receipt of said electron beam for producing an output signal representative of the shape of the selected character aperture, said target means being positioned relative to said beam deflection system and said first means for intercepting said electron beam.

4. In a cathode-ray writing tube, the combination comprising: electron beam generating means for selectively generating an electron beam; a character selection stencil having a convex-shaped face with a plurality of character apertures positioned at a corresponding plurality of predetermined positions therein, said stencil being positioned relative to said beam generating means such that said convex-shaped face faces the oncoming electron beam; a beam deflection system vfor cleflecting said electron beam to pass through a selected one of said character apertures substantially normal to a plane defined by the edges of the selected aperture; target means positioned relative to said stencil for intercepting said electron beam from said stencil, said target means being responsive to the receipt of said electron beam for producing an output signal representative of the shape of the selected character aperture.

5. The combination defined in claim 4 wherein said target means includes apparatus for converting said output signal to a charge pattern having a cross-sectional configuration corresponding to the cross-sectional configuration of the selected character aperture.

6r. A high speed cathode-ray writing tube responsive to a coded intelligence signal :for lselectively producing an output signal representative of the configuration of a selected character, said tube comprising: an evacuated envelope having therein an electron beam generator operable for generating an electron beam `at one end `and a target responsive to the receipt of said electron beam for generating the output signal representative of the configuration of said electron beam at an opposite end; a character forming stencil having la convex shaped face with a plurality of character apertures positioned at -a corresponding p-lurality of predetermined positions in Isaid face, said stencil being positioned intermediate Said electron beam generator and said target with said convex `face facing said electron beam generator; deflection means -responsive to the -coded intelligence signal for selectively deflccting said electron beam to pass through a selected one of said character apertures substantially normal to a plane defined by the edges ofthe aperture; and accelerat-= ing means for accelerating said elect-ron beam to said target.

7. The combination defined in claim 6 wherein said convex shaped face has a constant radius of curvature.

8. The combination defined in claim 6 wherein a funnel- .shaped device is positioned intermediate said stencil and said target for channeling said electron beam to said target.

9. In a `cathode-ray writing tube, the combination cornprising: electron beam generating means for selectively generating an electron beam; a character stencil having `a convex `surface with a constant radius of curvature, said surface having a pair of character yapertures positioned at a pair of predetermined positions, respectively, therein; beam deiiection means for directing said electron beam through a selected one of said character apertures substantially normal to a plane `defined by the edges of the selected aperture and radially toward the center of curvature of said convex surface; and target means positioned relative to said stencil to intercept said electron beam from said stencil, said target means responsive to the receipt of said elect-ron beam for producing `an output signal representative of the shape of the selected character aperture.

10. The combination defined in claim 9 which further includes a funnel-shaped conductor having an aperture therein positioned intermediate said stencil and said target and operable in conjunction with said character stencil for convergently channeling said electron beam from the stencil along a predetermined path through the :funnel laperture to said target.

References Cited in the file of this patent UNITED STATES PATENTS 2,111,231 Von Ardenne Mar. 15, 1938 2,173,193 Zworykin Sept. 19, 1939 2,213,688 Broadway Sept. 3, 1940 2,275,017 McNaney Mar. 3, 1942 2,379,880 Burgess July 10, 1945 2,88,342 Frenkel Mar. 31, 1959 2,889,547 Wesley June 2, 1959 2,952,796 Crews Sept. 13, 1960 

1. IN A CATHODE-RAY WRITING TUBE WHEREIN A RELATIVELY HIGH INTENSITY ELECTRON BEAM IS UTILIZED TO ACTUATE A TARGET TO PRODUCE AN OUTPUT SIGNAL REPRESENTATIVE OF A CHARACTER SELECTED IN ACCORDANCE WITH A CODED INTELLIGENCE SIGNAL, THE COMBINATION COMPRISING: BEAM SHAPING MEANS HAVING A NON-PLANAR SURFACE WITH A PREDETERMINED NUMBER OF CHARACTER APERTURES POSITIONED THEREIN, SAID BEAM SHAPING MEANS INCLUDING APPARATUS RESPONSIVE TO THE CODED INTELLIGENCE SIGNAL FOR DEFLECTING THE ELECTRON BEAM TO PASS THE ELECTRON BEAM THROUGH A SELECTED ONE OF THE CHARACTER APERTURES SUBSTANTIALLY ORTHOGONAL TO A PLANE DEFINED BY THE EDGES THEREOF; FIRST MEANS OPERATING IN CONJUNCTION WITH THE BEAM SHAPING MEANS FOR CONVERGENTLY DIRECTING THE ELECTRON BEAM FROM THE SELECTED CHARACTER APERTURE ALONG A PREDETERMINED PATH TO THE TARGET WHEREBY THE TARGET IS ACTUATED TO PRODUCE THE OUTPUT SIGNAL HAVING THE CONFIGURATION OF THE SELECTED CHARACTER APERTURE. 